Gelatin subbing compositions containing ascorbic acid



Patented Feb. 8, 1949 GELATIN SUBBING COMPOSITIONS CON- TAINING ASCORBIC ACID (VITAMIN C) Frank J. Kaszuba, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 18, 1946, Serial No. 717,095

Claims.

This invention relates to photographic film and particularly to subbing compositions therefor.

It is known that a gelatino silver-halide emulsion will not adhere to an untreated film base. An intermediate or subcoating layer is necessary to prevent frilling of the gelatin layer when wet, or stripping when dry. Since hardened gelatin, as used for glass plates does not adhere to a film base, it is necessary to use a mixture of gelatin with an organic solvent for the material of the film base, such as acetone, ethyl acetate, an alcohol-ether or an alcohol-acetone mixture. Gelatin is insoluble in these organic solvents and the film base is insoluble in water, but it is possible to prepare dispersions consisting of gelatin in a mixture of one of the organic solvents and water with a volatile organic acid, such as acetic acid, and the like, as a dispersing agent.

Many volatile and non-volatile organic acids have heretofore been used as dispersing agents for the gelatin in subbing compositions. It has been found-however, that the use of these acids causes a decrease in sensitivity and artificial ageing of the gelatino silver-halide emulsion layer. This effect is due primarily to the acidic nature of the dispersing agent. Moreover, subbing solutions. containing a dispersing agent possessing acidic characteristics have a tendency to corrode the film-making machinery and the solvent recovery system which is customarily a part thereof.

The present invention has as an object to overcome the above-mentioned diificulties and to provide a, method of dispersing gelatin in a subbing composition by means of dispersing agents, which will not desensitize and artificially age the gelatino silver-halide emulsion layer and which will not corrode the film-making machinery or solvent recoverysystem connected therewith.

Another object is to provide a non-desensitizing, non-corrosive dispersing agent for gelatin in subbing compositions.

A further object is to provide a new type of gel solution in which the gelatin is dispersed by means of a non-desensitizing, non-corrosive dispersing agent, which has no adverse effect upon photographic gelatino silver-halide emulsions.

Other objects will appear from the following description.

These object are accomplished by the use, as

2 dispersing agents in gelatin subbing compositions, of ascorbic acid (the enol of the l-form of the 'ylactone of 2.4.5.6-tetrahydroxy-3-ketohexanoic acid), commonly referred to as vitamin C, and characterized by the following formula:

TTJ in ZED-( )11 HilOH stantially an organic solvent or mixture of such solvents may vary from 94.5% to 98.5%. All proportions are by weight.

The subbing compositions are made by mixing the components in various ways so as to form a free flowing composition which dries or sets Within a reasonable length of time and forms a thin layer on a film base. In general, it is desirable to dissolve the vitamin C (dispersing agent) in water and add to it the gelatin until the gelatin is dispersed. Slight Warming and agitation will facilitate the dispersion of the gelatin in the aqueous solution of the vitamin C. The organic solvent or mixtures thereof are then mixed with the aqueous dispersion of gelatin, and the solution thus obtained is deposited on a film base in any convenient manner, such as by beading, immersion; roll application, or otherwise, the sub-- bing operation preferably being carried out in connection with, or as a part of, the process of making the film support itself. The subbing solutions made up as above described are clear dis-- persions of gelatin in the solvent mixture.

The film bases used in accordance with this invention are the cellulose derivatives, e. g., cellulose nitrate, cellulose acetate, and other lower fatty acid esters of cellulose including simple and mixed esters, such as cellulose propionate, cellulose butyrate, cellulose acetate-propionate, cellulose acetate-butyrate and the iike, ethers of cellulose, such as the ethyl ether, benzyl ether, and the like, or of any film-forming polymer or resin, such as polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate of vinyl chloride and vinylidene chloride, and the like, superpolymers as described in United States Patents 2,071,250-2-3 and 2,130,948.

It will be appreciated that each different type of cellulose ester, ether and mixtures thereof,

including the synthetic linear superpolymers,

requires a slightly different solvent or solvent combination. The solvent or solvent mixture employed does not dissolve gelatin, but must be :such that it will have a solvent or at least a softening or swelling action on the film base :so as to stick or anchor the gelatin upon the area of the base which has been softened or swollen, and the term solven as used in the claims should be so construed. For example,

"with a cellulose acetate or a superpolymer base =glycerol-uchlorohydrin, a low molecular weight alcohol, e. g., methanol, ethanol, and the like, or a ketone, such as acetone, or a mixture of EIYCBIOI-a-QhlOIOhYdI'll'l, alcohol and acetone may be employed. The ratio of alcohol to acetone ranges from about 30-60% to 75-25%, respectively. With cellulose acetate-propionate film base, an alkyl ester, such as, for example, methyl acetate, ethyl acetate, butyl acetate, and the like, either alone or with methanol, glycerol-achlorohydrin or 1.4-dioxane, may be efiectively employed. The weight of glycerol-a-chlorohydrin employed may vary from 1% to 5%. It may be pointed out at this point that the nature of the organic solvent or solvent mixture is immaterial so long as it Wets or bites into the cellulose derivative and superpolymer film base material, and the term solvent as used in the claims should be so construed. Since the materials suitable for film base and their solvent properties are known, no difiiculty is presented. in selecting a suitable solvent or solvent mixture for use in the subbing compositions.

The invention will be further illustrated but is not intended to be limited by the following examples.

Example I A film base of cellulose acetate was coated with the following subbing solution:

Parts Gelatin 1.0 Water 2.0 VitaminC 0.3 Glycerol-mchlorohydrin 2.7 Methanol 32.0 Acetone 62.0

After the subbing layer had dried, the usual light-sensitive emulsion layer was coated directly on it. After exposure and processing the emulsion adhered tenaciously to the cellulose acetate film support.

Example If A film base of cellulose acetate-propionate having an acetyl content of was coated with the following subbing solution:

4 After the subbing layer had dried, the usual light-sensitive emulsion layer was coated directly on it. After exposure and processing the emulsion adhered tenaciously to the cellulose acetatepropionate film support.

Example III A film base prepared from poly(vinyl chloridevinyl acetate) was coated with the following subbing solution:

Parts Gelatin u- 1.0 Water 2.7 Vitamin C 0.3

Glycerol-a-chlorohydrin' 3.0 Methanol 40.0

Acetone 53.0

After the subbing layer had dried, the usual light-sensitive emulsion layer was coated directly on it. After exposure and processing, the emulsion adhered tenaciously to the synthetic linear superpolymer film support.

The specific coating solutions set forth in the above examples may be substituted by the following:

The photograph film bases produced according to the present invention werefound to be entirely satisfactory and to give the customary physical requirements, such as, extreme strength, flexibility, and good water-resistance. V V

The small quantity of vitamin C, which may remain with the gelatin after evaporation of the water and organic solvent from the subbing composition, has no adverse effect upon thelight sensitive emulsion layer, nor has the subbing composition any adverse effect upon the con-- tainers in which it is stored, or upon the coating equipment employed.

It will be understood that wherein the claims appended hereto, the term subbing is used,

that such is intended to include the operation.

of applying a subbing layer from any one of the subbing compositions prepared inaccordance with the present invention.

While I have herein disclosed certain preferred manners of performing my invention, I do not thereby desire or intend to limit myself solely thereto, for as heretofore stated, theprecise proportions of materials utilized may be varied and other materials having equivalent hemical properties may be employed if desired, without departing. from the spirit and scope of the invention as defined in the followingclaims.

l1 claim:

1. A gelatin compositionsuitable for subbing a photographic film support, which comprises from 0.5% to 1.5% of gelatin dispersed in from 94.5%-

to 98.5% of a solvent for said support by means ofiro'm 0205921 to' 1.0% of ascorbic acid.

2. A gelatin composition suitable for subbing a cellulose derivative film support, which comprises from 05% to 1.5% of gelatin dispersed in a mixture of 62.0% of acetone, 32.0% of methyl alcohol,

and 2.0% of water, by means of from 0.05% to 1.0% of ascorbic acid.

3. A gelatin com-position suitable for subbing a cellulose acetate film support, which comprises 1.0% of gelatin dispersed in a mixture of 62.0%

of acetone, 32.0% of methyl alcohol, and 2.0% of 10 water, by means of 0.3% of ascorbic acid,

4. A gelatin composition suitable for subbing a cellulose acetate-propionate film support, which comprises 0.7% of gelatin dispersed with a mixture of 55.0% of acetone, 40.0% of methyl alcohol, and 2.1% of water, by means of 0.2% of ascorbic acid.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,341,877 Middleton et a1 Feb. 15, 1944 2,313,570 Nadeau et a1 Mar. 9, 1943 

